Headers make a Z06 go permanently rich?

[Chalky]

Numerous sources claim that Z06 goes rich after adding headers. Supposedly to the tune of 11.5 to 1.

My questions is this: Is this a default wide-open reading or does the car go rich initially and then come back to a more favorable reading with some drive time?

 

[c4c5specialist]

HI there,
No, this does not happen, unless you are eliminating the cats.
Allthebest, c4c5

 

[Chalky]

I removed the pup cats but the other cats remain.

What is the typical A/F ratio in wide-open?

I have seen a stock 97 C5 pull an 11.5:1 on a dyno pul. This A/F ratio seems to be common. Is this normal?l

 

[c4c5specialist]

Hi there,
How are you measuring air fuel ratio????
Tech 2, Autotap, or widerange air fuel sensors???
And if you are using widerange sensors, are you measuring before or after converters??????
Normally, programming inside PCM is about 12 to 1 air fuel ratio.
Allthebest, c4c5

 

[Chalky]

A/F was measured using wideband sensor on Dynojet. All readings were with cats in place and at the exhaust tip.

I did see two C5's go through. One was highly modified with H/C, etc and the other was a stock 97 C5. Both pulled 11.5 A/F ratios. Neither ever approached 12:1.

 

[c4c5specialist]

Hi there,
Converters will skew the results, however, I would hazard that the actual mixture is about 12 to 1.
Allthebest, c4c5

 

[JBsC5]

I have headers..high flow cats ..and if I remember correctly the Tech II gave a very good reading...

I can't remember the numbers but I remember being told that the numbers were good..

I like the headers on the car..I'd say above 4200rpm the car sings nicely and you can feel the extra get up and go..

 

[TODD L GRIFFITH]

Headers and A/F ratio

You need more information. To really know if the car is rich or lean, you need more than a snap shot during a dyno pull or two. You really need a tool to measure, and monitor your short and long term fuel trims, and your O2 voltages, before and after the cats in real time, over many miles of driving, to really get a true understanding of what is going on. C5specialist is correct here, you may not be getting a correct reading, because of the removal of the pup cats has scewed the result. I bet that the manufacturer's engineer's selection of the rear O2's were not specified with the pup cats removed, that is why the reading is questionable.